Wave Research

1. Wave Research Experiential Science 11 Ben Snow, Stephen Horton, Bob Sharp

2. Introduction • The purpose of this study was to determine the shape and character of obstructions that would create standing stationary waves. (surf waves) • A secondary purpose was to determine shapes would not create obstruction to the main laminar flow of the river below the dam. • These data were to be used to develop site specific plans for creating surf waves for recreational use.

3. Topics of Discussion • To simulate wave and flow dynamics in the Yukon River we constructed a model of the River Bed. This model consists of a continuous circuit in which a sump pump is used to pump water into a tank feeding a 2.4 meter section of river bottom. This model was used to gain an understanding of how certain variables created different kinds of waves and flows. These variables were: • · Flow velocity (measured in meters per second) • · Angle of riverbed (whether on not a depression is present in the riverbed) • · Size of Obstruction used to create waves • · Shape of Obstruction used to create waves • By modifying these variables we were able to determine which environment created the best surf waves for use by Canoe/Kayakers.

4. Shapes creating wave formations • Four basic shapes were used for each of the three different flow rates. Following study of the four shapes and a depression, we attempted to find the shapes that would create optimal surf wave at a given velocity. • The four shapes we used were: • Square block • Steep hump • Uniform hump • Wedge

5. Surf Wave structures • River surf waves are characterized as waves that have a segment with an up-stream slope that are stationary relative to the shore. In our studies we were looking for wave exhibiting a steep and relatively long up-stream slope. We observed three forms of standing waves in our experiments

6. Laminar Flow into Pressure Wave • One group of waves was created when a laminar (smooth) flow moved into a relatively stationary water body. This form created a rolling turbulent wave with the smooth current flowing into and under the rolling turbulent wave. These were characteristically caused by laminar flow moving into a pressure wave caused by an obstruction to smooth down stream flow. Such waves are characteristically short with considerable turbulence on the upstream flow component.

7. Laminar up-slope waves • A second group of waves was created when a laminar (smooth) flowed up-hill often cresting in a turbulent rolling wave. Such waves are characteristically longer with a smooth upstream flow component. This form of smooth current flowing up-hill because of some deeper obstruction that did not create a pressure wave but allowed to flow to curve upward without turbulence.

8. Standing haystacks • The third group of waves was created when a deeper water disturbance created a set of standing waves (haystacks). These appeared to be created by substrate depressions rather than projecting obstructions

9. Best Wave Production • When we set out to design the best wave conditions, we combined elements of both obstruction and river base depressions. We conducted a wide variety of experiments adjusting velocity, shape and size of obstruction, depressions in the base, and width of obstruction across the stream flow. In general the following comments apply to each of these topics.

10. Velocity Affects on Wave Form • Stream flow had a considerable impact upon flow and wave patterns. Laminar flow was more readily maintained in faster flows. An up-hill component of waves was possible at moderate flow rates. Pressure waves were less turbulent and backed up further in slower flows. The river flows recorded at both the intake site and across from the generating station (at the location of the existing standing waves). These flow patterns show

11. Shape of Flow Obstruction • The more gentle wedge shapes with the taper facing up-stream produced the most effective laminar flows. The block and steep hump shapes created notable pressure waves. Depressions was used in conjunction with wedge shaped obstructions created a virtual water wedge. This configuration created the most effective standing waves in our models.

12. Size of Flow Obstruction • Size of obstruction: When the thickness of the wedge obstruction was less than the flow depth, smooth up-hill flow occurred. When the thickness of the wedge obstruction was greater than the flow depth, a pressure wave developed and no up-hill flow developed. All other shapes developed pressure waves even shapes half the depth of the flow.

13. Width of the Obstruction • Width of obstruction: Obstructions that went part way across the channel, accelerated flows around the end of the obstructions. When these were staggered, standing waves, often diagonal rolling forms, were created between these obstructions.

14. Conclusions from Stream Modeling • The stream channel provides insights into the cross-sectional patterns of wave forms. The photos show how manipulation of flow rates, shapes, sizes and placement of obstructions affect wave size and structure. While this stream models the hydrology of rivers, they have shown us that small adjustments of these features have dramatic wave outcomes. This suggests that any obstruction placed in the river should be arranged to be movable (up and down stream) and adjustable (up and down).

15. The first data set that was collected simulated a river with a flow velocity of 1.81 meters/second with a riverbed angle of 4.4 degrees. Three photos illustrate show the reaction of water to three basic shapes outline before. Block shape with pressure wave 1.8 Meter/sec Wave forms • hump shape with pressure wave • Wedge shape with laminar flow

16. The second data set that was collected simulated a river with a flow velocity of 1.81 meters/second shows our best wave models Two photos illustrate the shapes that we found created the best surf waves at this flow rate. Wedge, depression , wedge sequence created a deep, longer wave with a strong up-stream slope. This configuration provided our best surf wave. 1.8 Meter/sec Best Wave forms • Wedge, depression sequence created a shallow but, longer wave with a strong up-stream laminar slope

17. 1.3 Meter/sec Wave forms • The first data set that was collected simulated a river with a flow velocity of 1.3 meters/second with a riverbed angle of 3 degrees. Three photos illustrate show the reaction of water to three basic shapes outline before. • Block shape with pressure wave • Hump shape with pressure wave • Shallow wedge shape with pressure wave

18. 1.3 Meter/sec Best Wave forms • The second data set that was collected simulated a river with a flow velocity of 1.3 meters/second shows our best wave models Two photos illustrate the shapes that we found created the best surf waves. • Wedge below depression. This shape gave us the best surf wave at this flow rate. • Wedge, depression, wedge. This shape gave us the next best surf wave at this flow rate. Deeper flow over second wedge

19. 1.1 Meter/sec Wave forms • The first data set that was collected simulated a river with a flow velocity of 1.1 meters/second with a riverbed angle of 1 degrees. Three photos illustrate show the reaction of water to three basic shapes outline before. All form create a quite pressure that moves upstream 10 to 50 times the depth of the obstacle • Block shape with pressure wave • Hump shape with pressure wave • Shallow wedge shape with pressure wave

20. 1.1 Meter/sec Best Wave forms • The second data set that was collected simulated a river with a flow velocity of 1.1 meters/second shows our best wave model at this flow rate. The photos illustrate the shape that we found created the best surf waves. Only one form created a wave at this low a flow rate. • Wedge below depression. This shape gave us the best surf wave at this flow rate. The front of the pressure wave created a small surf wave.

21. Measurements of Waves on the Yukon • The data below shows the flow rates recorded at two locations on the Yukon River: At the up-stream weir and at the gap in the intake. • Location Flow m/sec depth • Gap in intake • top of gap 2.3 m/sec 1.5 m • gap mid point 2.8 m/sec 1.0 m • base of shoot 2.9 m/sec 2.1 m • Up-stream Weir • top of wave 2.0 m/sec .8 m • gap mid point of wave 2.9 m/sec .7 m • surf wave 3.0 m/sec .9 m • These flow rates are greater than those used in the models are the volumes. This suggests a more uniform laminar flow in wave structures.

22. Waves on the Yukon • The Photo below shows the the area in which flow rates were taken on the Yukon River

23. Conclusions • The flow at both intake and weir sites are suitable for creating surf waves. • Use of wedge shapes and depressions will produce the most effective wave. • Continued experimentation with the model and in smaller streams will provide additional useful information • Staggering, at distance from the shore and at depth, should provide surf waves at different water levels without creating a pressure wave that would back up the water toward the hydro site.

24. Recommendations • Use a combination of wedge shape forms and depressions to create the most effective wave. • Develop methods for adjusting the initial location of the underwater obstacles so that optimal wave forms may be determined by experimentation. • Develop staggered underwater obstructions to create surf waves at different water levels. • Discuss plans with Yukon Energy to demonstrate plans would not create a pressure wave that would back up the water toward the hydro site.